The FBI arrested Hong Minh Truong on Monday. Legal documents state that evidence exists at Truong’s home that ties him to the letters. Language in the letters led the FBI to determine that they came from one person.

In the fall of 2010, 17 schools in Houston ISD received similar letters with the North Texas postmark. They appeared to have been mailed to the schools alphabetically.

At this time, it is not known if there is a connection between the Houston mailings and Monday’s arrest, but a source close to the investigation tells NEWS 92 FM that the FBI isn’t ruling out anything.

The white powder proved to not be dangerous, and no injuries have come from the letters.